Methods, systems and apparatuses for network assisted interference cancellation and/or suppression (naics) in long-term evolution (lte) systems

ABSTRACT

A method implemented by a Wireless Transmit/Receive Unit (WTRU) includes receiving a DeModulation Interference Measurement (DM-IM) resource, determining an interference measurement based on the DM-IM resource, and demodulating a received signal based on the interference measurement. An interference is suppressed based on the interference measurement. At least one DM-IM resource is located in a Physical Resource Block (PRB). The DM-IM resource is located in a PRB allocated for the WTRU. The DM-IM resource is a plurality of DM-IM resources which form a DM-IM pattern, and the DM-IM pattern is located on a Physical Downlink Shared Channel (PDSCH) and/or an enhanced Physical Downlink Shared Channel (E-PDSCH) of at least one Long Term Evolution (LTE) subframe. The DM-IM resources are different for different Physical Resource Blocks (PRB) in the LTE subframe. The DM-IM is located in a Long Term Evolution (LTE) Resource Block (RB), and the DM-IM pattern is adjusted.

BACKGROUND Field

This application is related to wireless communication.

Related Art

Long Term Evolution (LTE)

LTE: Single Carrier

3^(rd) Generation Partnership Project (3GPP) long term evolution (LTE)Release 8 and/or 9 (LTE Rel-8/9) may support up to 100 Mbps in aDownlink (DL), and 50 Mbps in an Uplink (UL) for a 2×2 configuration.The LTE DL transmission scheme is based on an Orthogonal FrequencyDivision Multiple Access (OFDMA) air interface.

LTE Rel-8/9 and/or release 10 (collectively “LTE Rel-8/9/10”) systemssupport scalable transmission bandwidths (e.g., for purposes of flexibledeployment, etc.). Such scalable transmission bandwidths may include,for example, bandwidths of 1.4, 2.5, 5, 10, 15 and 20 megahertz (MHz).

In LTE Rel-8/9 (and as applicable to LTE Rel-10), each radio frame has aduration of 10 milliseconds (ms), and consists of 10 subframe each ofwhich is 1 ms. Each subframe consists of 2 timeslots of 0.5 ms each.There may be either seven (7) or six (6) OFDM symbols per timeslot. Theseven (7) symbols per timeslot are used with a normal cyclic prefixlength, and the six (6) symbols per timeslot are used with an extendedcyclic prefix length. Subcarrier spacing for the LTE Rel-8/9 system is15 kHz. A reduced subcarrier spacing mode using 7.5 kHz is alsopossible.

A resource element (RE) corresponds to one (1) subcarrier during one (1)OFDM symbol interval. Twelve (1) consecutive subcarriers during a 0.5 mstimeslot constitute one (1) Resource Block (RB). Therefore, with seven(7) symbols per timeslot, each RB consists of 1*7=84 REs. A DL carriermay range from six (6) RBs up to one-hundred ten (110) RBs correspondingto an overall scalable transmission bandwidth of roughly 1 MHz to 20MHz. Each transmission bandwidth, e.g., 1.4, 3, 5, 10 or 20 MHz,corresponds to a number of RBs.

A basic time domain unit for dynamic scheduling is one subframe, whichconsists of two consecutive timeslots. This is sometimes referred to asa resource block pair. Certain subcarriers on some OFDM symbols areallocated to carry pilot signals in the time/frequency grid. A number ofsubcarriers at edges of the transmission bandwidth are generally nottransmitted so as to comply with spectral mask requirements.

In LTE Rel-8/9, and in Rel-10 in single carrier configuration where thenetwork may assign the UE only one pair of UL and DL carriers (FDD) orone carrier time shared for UL and DL (TDD), for any given subframethere may be a single Hybrid Automatic Repeat reQuest (HARQ) processactive for the UL and a single HARQ process active in the DL.

LTE: Carrier Aggregation (CA)

LTE Advanced with Carrier Aggregation (LTE CA Rel-10) is an evolutionthat aims to improve single carrier LTE data rates using, among otherexamples, bandwidth extensions also referred to as carrier aggregation(CA). With CA, a user equipment (UE) may transmit and receivesimultaneously over a Physical Uplink Shared Channel (PUSCH) and aPhysical Downlink Shared Channel (PDSCH) (respectively) of multipleserving cells. For example, up to four secondary serving cells (SCells)may be used in addition to a primary serving cell (PCell), thussupporting flexible bandwidth assignments up to 100 MHz. Uplink ControlInformation (UCI), which may include HARQ acknowledgment and/or nonacknowledgement (ACK/NACK) feedback and/or channel state information(CSI), may be transmitted either on a physical uplink control channel(PUCCH) resources of the PCell or on PUSCH resources available for aserving cell configured for UL transmissions.

Control information for scheduling of PDSCH and PUSCH may be sent on oneor more physical data control channel(s) (PDCCH). In addition to LTERel-8/9 scheduling using one PDCCH for a pair of UL and DL carriers,cross carrier scheduling may also be supported by a given PDCCH;allowing the network to provide PDSCH assignments and/or PUSCH grantsfor transmissions in one or more other serving cells.

For a FDD LTE Rel-10 UE operating with CA, there may be one HARQ entityfor each serving cell. Each HARQ entity may have up to 8 HARQ processes,e.g., one per subframe for one round trip time (RTT). Further, for theFDD LTE Rel-10 UE operating with CA, there may be more than one HARQprocess active for the UL and for the DL in any given subframe. However,there may be at most one UL and one DL HARQ process per configuredserving cell.

It is expected that the capacity needs of currently deployed wirelessnetworks may continue to grow at an exponential pace as the use ofwireless devices continues to explode globally. In order to boost thecapacity of networks and dense cell deployments (i.e., via the use oftighter macro cell deployment or via the use of small cells), improvedcell spectral efficiency may be required. Such new deployments may comeat the cost of increasing the overall interference landscape. To improvethe performance of such high interference deployments, previous effortshave focused on improving the CSI feedback from User Equipment (UE) inorder to better enable an evolved NodeB (eNB) to select transmissiontechniques that are the most advantageous for each UE. For example, inRelease-11 interference measurement resources in the form of CSIInterference Measurement (CSI-IM) could be introduced, enabling anetwork to clearly instruct each UE how to measure interference fordifferent transmission hypotheses. Another method for improving theperformance of UEs in highly interfering environments could be achievedunder Enhanced Inter-Cell Interference Coordination (eICIC) techniquesin Release-10. In this case, a UE served by a Pico cell could beconfigured with two sets of measurements. Each set of measurements couldhave a defined subset of subframes upon which a UE could perform CSImeasurements. This could allow a network to potentially use Almost BlankSubframes (ABS) from an interfering cell in order to ensure that the UEcould sometimes be served in a reduced interference environment. InRelease-11eICIC was extended by using Further Enhanced Inter-CellInterference Coordination (FeICIC). This study focused on the use ofnonlinear interference cancellation receivers to mitigate strong Cellspecific Reference Signal (CRS)/Primary Synchronization Signal(PSS)/Secondary Synchronization Signal (SSS)/Physical Broadcast Channel(PBCH) interference. For example, up to two interfering CRStransmissions can be cancelled at the UE by having the network indicatethe resources upon which the UE should expect such interfering CRS.

In Long Term Evolution (LTE) systems, advanced UE receivers may be usedto improve the performance of downlink transmission. Such advanced UEreceivers may enable interference cancellation or suppression. Byefficiently cancelling or suppressing interference, the Signal toInterference plus Noise Ratio (SINR) of the desired transport block maybe increased and thus, higher throughput may be achieved. Some examplesof advanced receivers include Minimum Mean Square Error/InterferenceRejection Combiner (MMSE-IRC), Widely Linear (WL) MMSE-IRC, SuccessiveInterference Cancellation (SIC) and Maximum Likelihood (ML).

SUMMARY

A method implemented by a Wireless Transmit/Receive Unit (WTRU) includesreceiving a DeModulation Interference Measurement (DM-IM) resource,determining an interference measurement based on the DM-IM resource, anddemodulating a received signal based on the interference measurement. Aninterference is suppressed based on the interference measurement. Atleast one DM-IM resource is located in a Physical Resource Block (PRB).The at least one DM-IM resource is located in a PRB allocated for theWTRU. The DM-IM resource is a plurality of DM-IM resources, theplurality of DM-IM resources form a DM-IM pattern, and the DM-IM patternis located on at least one of a Physical Downlink Shared Channel (PDSCH)and/or an enhanced Physical Downlink Shared Channel (E-PDSCH) of atleast one Long Term Evolution (LTE) subframe. The DM-IM resources aredifferent for different Physical Resource Blocks (PRB) in the LTEsubframe. The DM-IM is located in a Long Term Evolution (LTE) ResourceBlock (RB), and the method includes adjusting a DM-IM pattern based onat least one of a frame number associated with the LTE RB, a subframenumber associated with the LTE RB, and/or an RB index associated withthe LTE RB. A plurality of DM-IM resources is received, and the DM-IMresources are adjusted in respective LTE subframes based on a higherlayer signaling. Locating a DM-IM resource associated with the WTRUbased on a cell specific identifier associated with a cell serving theWTRU is performed.

A Wireless Transmit/Receive Unit (WTRU) includes a receiver configuredto receive a DeModulation Interference Measurement (DM-IM) resource, anda processor configured to determine an interference measurement based onthe DM-IM resource, and demodulate a received signal based on theinterference measurement. The processor is father configured to suppressan interference based on the interference measurement. At least oneDM-IM resource is located in a Physical Resource Block (PRB). The atleast one DM-IM resource is located in a PRB allocated for the WTRU. TheDM-IM resource is a plurality of DM-IM resources, the plurality of DM-IMresources form a DM-IM pattern, and the DM-IM pattern is located on atleast one of a Physical Downlink Shared Channel (PDSCH) and/or anenhanced Physical Downlink Shared Channel (E-PDSCH) of at least one LongTerm Evolution (LTE) subframe. The DM-IM resources are different fordifferent Physical Resource Blocks (PRB) in the LTE subframe. The DM-IMis located in a Long Term Evolution (LTE) Resource Block (RB), and theprocessor is father configured to adjust a DM-IM pattern in a LTEResource Block (RB) based on at least one of a frame number associatedwith the LTE RB, a subframe number associated with the LTE RB, and/or anRB index associated with the LTE RB. The processor is father configuredto receive a plurality of DM-IM resources, and adjust a number of DM-IMresources in a respective LTE subframe based on a higher layersignaling. The processor is father configured to locate a DM-IM resourceassociated with the WTRU based on a cell specific identifier associatedwith a cell serving the WTRU.

A method implemented by a Wireless Transmit/Receive Unit (WTRU) includesreceiving a Downlink (DL) information, and determining, from the DLinformation, whether a co-scheduling indicator indicates that a furtherWTRU or transmitter is co-scheduled with the WTRU. An Interfering Signal(IS) of the further WTRU or transmitter is suppressed based on theco-scheduling indicator.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the detailed descriptionbelow, given by way of example in conjunction with drawings appendedhereto. Figures in such drawings, like the detailed description, areexamples. As such, the Figures and the detailed description are not tobe considered limiting, and other equally effective examples arepossible and likely. Furthermore, like reference numerals in the Figuresindicate like elements, and wherein:

FIG. 1A is a diagram of an example communications system in which one ormore disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 1D is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A;

FIG. 1E is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A;

FIG. 2 is a schematic representation of a demodulation interferencemeasurement pattern;

FIG. 3 is a schematic representation of the RE locations for two CDMgroups of DM-RS ports;

FIG. 4 is a table setting forth the modulation schemes of a complexvalued modulation scheme and a real valued modulation scheme accordingto the modulation order and/or bit width; and

FIG. 5 is an example of an M-ary PAM for the M=2 and M=4 cases.

FIG. 6 is a flow diagram of an interference suppression process whichmay be performed in accordance with the present invention.

FIG. 7 is a flow diagram of an interference suppression process whichmay be performed in accordance with the present invention.

FIG. 8 is a flow diagram of an interference suppression process whichmay be performed in accordance with the present invention.

FIG. 9 is a flow diagram of an interference suppression process whichmay be performed in accordance with the present invention.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a thorough understanding of embodiments and/or examplesdisclosed herein. However, it may be understood that such embodimentsand examples may be practiced without some or all of the specificdetails set forth herein. In other instances, well known methods,procedures, components and circuits have not been described in detail,so as not to obscure the following description. Further, embodiments andexamples not specifically described herein may be practiced in lieu of,or in combination with, the embodiments and other examples disclosedherein.

Example Architecture

When referred to herein, the terms “user equipment” and its abbreviation“UE” may mean (i) a wireless transmit and/or receive unit (WTRU), suchas described infra; (ii) any of a number of embodiments of a WTRU, suchas described infra; (iii) a wireless capable and/or wired capable (e.g.,tetherable) device configured with, inter alia, some or all structuresand functionality of a WTRU, such as described infra; (iii) a wirelesscapable and/or wired capable device configured with less than allstructures and functionality of a WTRU, such as described infra; or (iv)the like. Details of an example WTRU, which may be representative of anyUE recited herein, are provided below with respect to FIGS. 1A-1C.

When referred to herein, the terms “evolved Node-B” and itsabbreviations “eNB” and “eNode-B” may mean (i) a base station, such asdescribed infra; (ii) any of a number of embodiments of a base station,such as described infra; (iii) a device configured with, inter alia,some or all structures and functionality of a base station or eNB, suchas described infra; (iii) a device configured with less than allstructures and functionality of a base station or eNB, such as describedinfra; or (iv) the like. Details of an example eNB, which may berepresentative of any eNB recited herein, are provided below withrespect to FIGS. 1A-1C.

When referred to herein, the terms “mobility management entity” and itsabbreviation “MME” may mean (i) an MME, such as described infra; (ii) anMME in accordance with a 3GPP LTE release; (iii) an MME in accordancewith a 3GPP LTE release modified, extended and/or enhanced according tothe description that follows; (iii) a device configured with, interalia, some or all structures and functionality of any of theaforementioned MMEs; (iv) a device configured with less than allstructures and functionality of any of the MMEs of (i) and (ii) above;or (iv) the like. Details of an example MME, which may be representativeof any MME recited herein, are provided below with respect to FIGS.1A-1C.

When referred to herein, the term “at least one” may mean “one or more.”

FIG. 1A is a diagram of an example communications system 1100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a tablet computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High Speed DownlinkPacket Access (HSDPA) and/or High Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 19, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 19 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 116. The RAN 104 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 104 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 104. TheRAN 104 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 104 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 104 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 104 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 106, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 106 and the PSTN 108. In addition, the corenetwork 106 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 104 and the core network 106according to an embodiment. The RAN 104 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 116. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 104, andthe core network 106 may be defined as reference points.

As shown in FIG. 1E, the RAN 104 may include base stations 170 a, 170 b,170 c, and an ASN gateway 142, though it will be appreciated that theRAN 104 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 170 a, 170 b,170 c may each be associated with a particular cell (not shown) in theRAN 104 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 116. In oneembodiment, the base stations 170 a, 170 b, 170 c may implement MIMOtechnology. Thus, the base station 170 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 170 a, 170 b, 170 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 142 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 106, and the like.

The air interface 116 between the WTRUs 102 a, 102 b, 102 c and the RAN104 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 106.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 106 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 170 a, 170 b,170 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 170 a, 170 b,170 c and the ASN gateway 142 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 104 may be connected to the core network106. The communication link between the RAN 104 and the core network 106may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 106 may include a mobile IP home agent(MIP-HA) 144, an authentication, authorization, accounting (AAA) server146, and a gateway 148. While each of the foregoing elements aredepicted as part of the core network 106, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA 144 may be responsible for IP address management, and mayenable the WTRUs 102 a, 102 b, 102 c to roam between different ASNsand/or different core networks. The MIP-HA 144 may provide the WTRUs 102a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices. The AAA server 146 may be responsiblefor user authentication and for supporting user services. The gateway148 may facilitate interworking with other networks. For example, thegateway 148 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 148 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 11,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 104may be connected to other ASNs and the core network 106 may be connectedto other core networks. The communication link between the RAN 104 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 104 and the other ASNs. The communication link betweenthe core network 106 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

Overview

Methods, systems and apparatus for user equipment (UE) and networkoperation in view of a New Carrier Type (NCT) in long-term evolution(LTE) systems may be disclosed. At least some of the methods, systemsand apparatus may be directed to supporting operation with the NCT,including, for example, methods, systems and apparatus for paging, cellre-selection and measurements, radio link monitoring, system informationacquisition, and cell type detection.

Among the aforementioned methods, systems and apparatus is a method thatmay include selectively mixing a NCT subframe with one or more othersubframe types in a (same) carrier. The carrier may be a NCT carrier ora legacy carrier. In certain embodiments, the legacy carrier may bedefined in accordance with at least one release of 3rd generationpartnership project (3GPP) technical specification(s) (TS(s)) directedto Long-Term Evolution (LTE) prior to release twelve (12) of the 3GPPTSs (collectively “3GPP LTE pre-Rel-12”). In certain embodiments, theNCT carrier may be defined according to at least one protocol differentfrom the legacy carrier.

The NCT subframe may be, or include at least a portion of, a subframedefined according to at least one protocol different from legacysubframe types. The NCT subframe, for example, may be a CRS-lesssubframe, a CRS-limited subframe, a limited port CRS subframe, aDemodulation Reference Signal (DM-RS) subframe, a non-backwardcompatible subframe and a mixed NCT subframe.

The other subframe types may be non-NCT subframes. The non-NCT subframesmay include the legacy subframe types. The legacy subframe types may bedefined in accordance with 3GPP LTE pre-Rel-12. Examples of the non-NCTsubframes may include a normal (e.g., UL and/or DL) subframe, a specialsubframe, a multimedia broadcast multicast services (MBMS)single-frequency network (SFN) (MBSFN) subframe and an ABS.

Overview of LTE Procedures

System Information Acquisition

According to 3GPP TS 36.133, section 8.1.2.2.4.1, a UE in connected modethat is configured to perform measurements on a frequency thatcorresponds to a neighbor cell might not (or might not be required to)read master information block(s) (MIB(s)) and/or system informationblocks (SIB(s)) of neighbor cells unless the UE is explicitly instructedto read such information for associated measurement reportConfig (e.g.,using an si-RequestForHO parameter). Cell global identity (CGI)detection may require acquisition of the MIB and/or the SIB1, however.

Measurements in Connected Mode

Measurements may be typically used for mobility control, for radio linkmonitoring and for power settings.

A UE may make a number of measurements of and/or using CRS (or common)reference signals (CRS). The UE may use the measurements to determine,for example, radio quality of one or more LTE cells. Examples of themeasurements include any of a RS received power (RSRP) measurement, areference signal received quality (RSRQ) measurement, a receive strengthsignal indicator (RSSI) measurement and a DL path loss (PL) estimation(which may be based on an RSRP measurement). The UE may make themeasurements in accordance with requirements that specify a certainlevel of accuracy. In accordance with such requirements, a UE may assumethat the CRS may be present in every DL subframe and at least one DLsubframe may be measured per radio frame using at least those CRS. TheUE may be configured with a parameter that restricts the DL subframes onwhich to perform measurements for a frequency of a serving cell. Anexample of such parameter may be measSubframePatternConfigNeighparameter.

Layer 3 (L3) filtering may be configured per measurement quantity, e.g.,per RAT type. A filtering period applied typically serves to adjust(e.g., on a sliding scale) an amount of instances a handover may occurand/or handover delay. Such filtering period may be a function of UEvelocity. A short filtering period may lead to a low handover delay, butto a high handover rate. A long filtering period (e.g., longer induration that the short filtering period) may lead to high handoverdelay and/or low handover rate. A higher number of samples permeasurement (e.g. within a measurement gap, if configured) may improvethe measurement accuracy, and may contribute to lower the rate ofhandover. A filter coefficient may be configured per measurement type(e.g., for a RSRP measurement, a RSRQ measurement, a RSSI measurement,DL PL estimation, etc.).

The RSRP and/or RSRQ measurements may be typically needed by the UE todetect a cell. For DL PL estimation, filtering may also be configuredand applied per serving cell.

Radio Link Monitoring (RLM) and Measurements in Connected mode

For a PCell, the UE may perform radio link monitoring (RLM). The UE maydo so by estimating a problem error rate for reception of a hypotheticalPDCCH, including Physical Control Format Indicator Channel (PCFICH)errors. The UE may perform measurements over a 200 ms period, and mayset the error rate at 2% for Q_(in) and at 10% for Q_(out). The UE mayapply any subframe restrictions in time for RLM measurements. The UEmight require at least one measurable subframe per radio frame for RLM.

Measurements and Cell Reselection

In idle mode, the UE may perform measurements of a current serving cellon which it has camped, and of neighboring cells on both (i) the samecarrier frequency, e.g., intra-frequency, and (ii) different carrierfrequencies, e.g., inter-frequency.

A serving eNB may provide information concerning neighboring cellinformation for measurements in its system broadcast information and/orvia dedicated signaling, such as, for example, Radio Resource Control(RRC) signaling. The serving eNB may provide dedicated priorityinformation (e.g., by cell list) through dedicated RRC signaling. The UEmay detect and measure cells that may not be part of a provided celllist. To limit the amount of measurements that the UE has to carry outand/or to minimize battery consumption during a DRX cycle of the UE, forexample, the UE may use the priorities assigned to certain frequencieswhen determining when to measure and which cells to measure forinter-frequency and intra-frequency neighbor cell measurements.

The UE may make neighbor measurements as follows (or as set forth in atleast one of the following):

-   -   for frequencies assigned a higher priority than a current        frequency, the UE may perform inter-frequency measurements on        cells in that higher priority frequency;    -   for frequencies assigned a priority equal or lower than a        current frequency, the UE may perform inter-frequency        measurements after RSRP and/or RSRQ measurement(s) of the        current cell fall below respective specified thresholds; and    -   the UE may perform intra-frequency measurements after the RSRP        and/or RSRQ measurement(s) of the current cell fall below        respective specified thresholds.

The measurements of neighboring cells may be monitored and evaluated bythe UE in idle mode, and the UE may decide to perform cell re-selectionto another cell when the cell re-selection criteria are met, whereinmeeting such cell re-selection criteria is based on one or morethresholds, which may be provided in system information.

DRX/Paging

The network may use a paging message to reach or communicate with the UEin idle mode. The paging message may include information that may be UEspecific and/or general indicators. The UE-specific information may beand/or include, e.g., information for establishing a connection to thenetwork. The general indicators may be and/or include, e.g., indicatorsfor notifying the UE (and other UEs) of changes to certain broadcastinformation of the cell, including, e.g., earthquake and tsunami warningsystem (ETWS) information and/or commercial mobile alert system (CMAS)information. To minimize an amount of time the UE needs to look for apossible page, a DRX cycle and paging occasions may be assigned to theUE either through cell system information or through higher layerspecified parameters. Paging information may be sent on certainsubframes on a PDSCH whose resource location may be sent on a PDCCHmasked with paging radio network temporary identifier(s) (P-RNTI). Giventhat a single P-RNTI assigned to a cell, a single paging message may besent on the pre-assigned subframes, and such paging message may includepaging information for one or more UEs.

LTE Operation Modes

In a FDD mode of operation, different carriers may be used for UL and DLtransmissions, and a UE (e.g., a UE capable of full duplexcommunication) may simultaneously receive in the DL and transmit in theUL. In a TDD mode of operation, UL and DL transmissions may be carriedon the same carrier frequency separated in time. For a given carrier, aUE operating under TDD does not simultaneously receive in the DL andtransmit in the UL.

For efficient operation, some implementations of advanced receivers mayrequire more information at the UE. For example, Successive InterferenceInterference (SIC) may be improved if a UE may also be aware of theparameters of the Interfering Signals (IS) (such as RB allocation, theModulation and Coding Scheme (MCS), etc. . . . ). The network may enablesuch efficient interference cancellation or suppression by assisting theUE.

Network Assisted Interference Cancellation and/or Suppression (NAICS)may enhance the performance of data channels (e.g., PDSCH) as well assome control channels of interest. Some issues that may arise in theimplementation of enhanced decoding schemes, for example NAICS, mayinclude signaling features for enabling more effective and robustUE-side interference cancellation and/or suppression. This may includehow such signaling may be performed, as well as what such signalingentails. Furthermore, NAICS may not be relevant under all transmissionscenarios. Therefore, methods for triggering NAICS may be required.Another issue that may arise may be how to design modulation to betterenable the optimal improvement of advanced UE receivers.

Delivery of information to a receiver to support the implementation ofNAICS functionality may result in significant design issues to overcome.For example, in the context of HSPA UEs and networks, downlink commoncontrol channels like High Speed Synchronization Control Channels(HS-SCCH), may be used to convey information. The information conveyedmay be information about an interferer for a UE attempting to canceldata traffic channel interference on the High Speed Downlink SharedChannel (HS-DSCH). A NAICS capable UE may learn about the UE identifierof its strongest interferer and decode the HS-DSCH schedulinginformation for the interferer from the associated HS-SCCH for thatinterferer. In LTE networks a NAICS capable handset may account for thepossible presence of one out of many candidate interfering UEs on the RBallocated to its DL data channel in a subframe, i.e., the PDSCH. Thismay be so due to differences in DL control channel design, and theflexibility of the Frequency Division Multiplexing/Time DivisionMultiplexing (FDM/TDM) scheduling approach. In particular, many UEs maybe possible candidates for scheduling by the eNB. Any of the possiblecandidates may become interferers for the UE under consideration.However, decoding all DL assignment messages in a given subframe for allpossible candidate interferer UEs may be an overwhelmingly complex taskfor a NAIC capable UE to accomplish. It may be overwhelmingly complexeven if the device is aware of all other UE identifiers. Similarly,restricting the list of candidate interferers to reduce the decodingcomplexity for the NAICS capable UE could significantly adversely affectsystem throughput as a consequence of scheduling/co-schedulinglimitations. Therefore, methods and procedures may be sought that couldallow a NAICS capable handset to obtain information about candidateinterfering UEs in a given transmission time interval. The methods andprocedures may allow for low complexity implementation in the NAICScapable handset, while not limiting system performance from the basestation perspective.

Possible Examples

Examples described herein may be used by a UE or a UE method in anycombination to improve the decoding performance of DL channelsincluding, but not limited to, PDSCH, PDCCH, E-PDCCH or a newly defineddownlink physical channel. Corresponding methods may be performed bypoints within a network communicating with the UE or UE method. Theexamples may be effective through techniques such as interferencesuppression or cancellation. The term “desired information” may be usedto refer to any Downlink Control Information (DCI) or higher layer data(i.e., information bits from a transport channel such as DL-SCH) thatthe IE may have to receive from the DL physical channels. The term“enhanced decoding scheme” may be used to generally refer to anyprocedure for obtaining the desired information that employs an exampledescribed herein. The terms NAIC or NAICS may also be used to refer tosuch procedures or enhanced deciding schemes. The term NAICS capable UEmay be used to refer to a UE that may employ such any such procedure.

In some examples, the UE may determine or obtain information on at leastone downlink signal, an IS. The IS may be received in the same subframeas its desired information. The UE may use the obtained informationabout the IS, such as its transmission parameters, to improve theprobability of successful decoding of its received signal. It may useany possible interference cancellation techniques or any combination ofinterference cancellation techniques. This information may be referredto as IS information herein.

In some examples, the UE may perform a measurement to estimateproperties of an IS received in the same subframe as its desiredinformation. The result of the measurement may be used to improve theprobability of successful decoding in the subframe through techniquessuch as interference suppression. The measurement may be different frominterference measurements carried out for the purpose of CSI reporting(e.g., CSI-IM). The UE may be provided with a resource to perform such ameasurement. The resource may be referred to as DM-IM herein.

In some examples, the UE may decode its desired information according toa different modulation scheme to facilitate the use of techniques suchas interference suppression. A new downlink physical channel may bedefined for such operation. For example, the UE may receive at leastDL-SCH information from an enhanced PDSCH (E-PDSCH) according tophysical layer processing (e.g., modulation scheme) different than forPDSCH.

In some examples, the UE may employ new procedures to support operationswith the enhanced decoding scheme. According to these procedures the UEmay, for example, determine whether to attempt decoding according to anenhanced decoding scheme in a particular subframe. It may also determinehow to provide Hybrid Automatic Repeat Request (HARQ) feedback. The UEmay also enhance functionalities such as CSI feedback to better supportthe enhanced decoding scheme.

Interference Suppression

DM-IM Resource

A UE May Perform Measurements of Interference on a Defined Resource,(e.g., DM-IM), for Demodulation Purposes

A resource for interference measurement may be defined. A UE may measurethe interference from the resource. It may use the measurement whendemodulating a received signal for its desired information, for example,in a receiver such as an MMSE-IRC type of receiver. The UE may use themeasurement for interference suppression.

A RE for interference measurement may be defined as a DM-IM. The UE maymeasure the interference. It may, for example, use the measurement fordemodulation. One or more DM-IM may be located in the Physical ResourceBlock (PRB) pairs allocated for a UE to receive PDSCH. The UE maymeasure interference from the one or more of the DM-IM within the PRBpairs allocated for the UE.

The DM-IM may be defined as a null RE, i.e., a RE onto which no symbolfrom PDSCH, E-PDSCH or other physical channel may be mapped. Whendemapping REs to modulation symbols for a physical channel, the UE mayassume that no symbol may be mapped to REs used for DM-IM (i.e., ratematching). The UE may also assume that puncturing is applied on codedbits corresponding to symbols that are mapped to the REs.

DM-IM Collision Handling

A DM-IM may be defined as any PDSCH RE location. One or more of thefollowing may apply when the DM-IM collides with another signal. If anonzero power CSI-RS RE may be overlapped with a DM-IM, the nonzeropower CSI-RS RE may have higher priority. Thus, a UE may assume thatnonzero power CSI-RS may be transmitted in that RE.

If a zero power CSI-RS RE may be overlapped with a DM-IM, a UE mayassume that the RE may be used as a DM-IM. The UE may measureinterference from the DM-IMs including a DM-IM that collides with a zeropower CSI-RS RE. It may use the interference information fordemodulation. Alternatively, if a zero power CSI-RS RE may be overlappedwith a DM-IM, the zero power CSI-RS RE may have higher priority. Thus,the UE may not include a DM-IM colliding with a zero power CSI-RS RE forinterference measurement.

If a CSI-IM RE may be overlapped with a DM-IM, a UE may assume that theRE may be used for both CSI-IM RE and DM-IM. The UE may use the RE forinterference measurement for CSI feedback and/or interferencemeasurement for demodulation.

If a Positioning Reference Signal (PRS) RE may be overlapped with aDM-IM, the PRS RE may have higher priority. A UE may assume that the REmay be used for a PRS. A UE may not include a DM-IM colliding with a PRSRE for interference measurement.

If a Primary Synchronization Signal (PSS) or a Secondary SynchronizationSignal (SSS) RE may be overlapped with a DM-IM, the PSS/SSS RE may havehigher priority. A UE may not include a DM-IM colliding with a PSS orSSS RE for interference measurement. Alternatively, a UE may assume thatDM-IM may not be used in a PRB pair containing PSS/SSS.

DM-IM Pattern

Referring now to FIG. 2 , there is shown a schematic representation of ademodulation interference measurement pattern 200. The demodulationinterference measurement pattern 200 may show a PRB pair, consisting ofPRBs such as PRB 200 a and PRB 200 b. Each PRB 200 a, b may include aplurality of DM-IM patterns. Any other types of symbols may be presentin a PRBa, b, such as DM-RS, a CRS and/or a PDCCH. In one possibleexample, a fixed number of DM-IMs may be used in a DM-IM pattern 200.Multiple patterns of DM-IM pattern 200 may be defined to be orthogonalor quasi-orthogonal. DM-IM pattern 200 may include any number ofInterference Measurement Resource Elements (IM-RE) patterns, such asIM-RE pattern 1, IM-RE pattern 2, or IM-RE pattern 3, as shown in FIG. 2. The IM-RE patterns 1, 2, 3 may be orthogonal. Furthermore, one or moreof followings may apply.

A DM-IM pattern may be defined in the PRB pair. In general, N DM-IMs maybe used per PRB pair. The N DM-IMs may be located in a distributedmanner or a localized manner within a PRB pair.

The number of DM-IMs per PRB pair, N, may be predefined. Alternately, itmay be configured, for example, by higher layer signaling.

Multiple DM-IM patterns which may be orthogonal may be defined. Thenumber of DM-IM patterns may be a function of N.

One or more sets of DM-IM patterns may be defined. For a certain set ofDM-IM patterns, the patterns in the set, e.g., all the patterns in theset, may have the same number, N, of DM-IMs per PRB pair. The number ofpatterns in the set may be a function of N. Alternately, the maximumnumber of patterns in the set may be a function of N.

The number of available DM-IM patterns within each DM-IM pattern set maybe different. For instance, if N is large the number of available DM-IMpatterns may be smaller, as compared with the DM-IM pattern typescorresponding to a smaller N.

The number of available DM-IM patterns in each DM-IM pattern set may bedifferent. For instance, if N is large, the number of available DM-IMpatterns may be smaller as compared with the DM-IM pattern typecorresponding to smaller N.

One or more sets of DM-IM patterns may be defined. The DM-IM patterns ina set may be mutually orthogonal in time and/or frequency locationwithin a PRB pair. For instance, the RE locations for DM-IM pattern 1may be mutually orthogonal with DM-IM pattern 2 in time and/or frequencylocation.

The DM-IM pattern(s) in a cell may be a function of at least one of cellID, virtual cell ID, or another cell related signal or parameter.

One or more sets of DM-IM patterns may be a function of cell ID, virtualcell ID, or another cell related signal or parameter.

A set of DM-IM patterns may be split into any number of multiple subsetsof DM-IM patterns. A different subset of DM-IM patterns may be usedaccording to the cell or virtual cell. As an example, a subset of DM-IMpatterns may be configured to a specific cell as a function of physicalcell ID and/or virtual cell ID. There may be S subsets (or sets) ofDM-IM patterns, where the subset (or set) index s=0, 1, . . . , S−1. Theindex may be configured as a function of the physical/virtual cell ID.For example, a modulo operation may be used to configure the subset (orset) of indexes, such as s=cell ID mod S.

A UE may be provided with or configured with, e.g., via RRC signaling,one or more sets of DM-IM patterns or parameters. The UE may determineone or more sets of DM-IM patterns from the DM-IM patterns orparameters.

A DM-IM pattern may be configured, for example, in a UE specific manner.

The DM-IM pattern to be used by a UE may be configured semistatistcallyvia higher layer signaling such as RRC signaling or it may be configureddynamically. Dynamic configuration may be via an indication which may bein a DCI format. This format may provide a grant for the PDSCH. Thegrant may include the DM-IMs in the indicated pattern. For example, if KDM-IM patterns may be available, for example in general or for a givenserving cell, the DM-IM pattern index k may be configured via higherlayer or physical layer signaling. The value of index k may be 0, 1, . .. , K−1.

The configuration of a DM-IM pattern may include any one or moreparameters that may enable the UE to determine which pattern to use,such as one or more of the following. The configuration may be anindication of which pattern set of a group of predefined or configuredsets of patterns to use. The configuration may be an indication of whichpattern of a predefined or configured set of patterns to use. Theconfiguration may be the value of N. The configuration may be anindication of a value of N from a set of N values which may be known tothe UE, e.g., by definition or configuration. For example, if thepossible values of N are 4, 8, 16, and 32, the value of N may beindicated by two bits to select one of the 4 choices.

The DM-IM pattern may be determined in a UE specific manner. Forinstance, if K DM-IM patterns may be available, for example in generalor for a given serving cell, the DM-IM pattern to be used by a specificUE may be a function of the Cell Radio Network Temporary Identifier(C-RNTI) of the UE. As an example, a modulo operation may be used withC-RNTI and the number of available DM-IM patterns. For example, theDM-IM pattern index k, where k may be 0, 1, . . . , K−1, may bedetermined by the UE from: k=C-RNTI mod K.

A DM-IM pattern may be defined within a PRB pair in a UE-specificmanner. The DM-IM pattern for the UE may be defined as a function ofC-RNTI. As an example, the C-RNTI may be used as an initializationparameter for a sequence generation, and the generated sequence may beused as a DM-IM pattern. The sequence may indicate the N DM-IM locationswithin a PRB pair. This may require a set of RE indexes for the REs forPDSCH. This may be applicable for the case of quasi-orthogonal DM-IMpatterns.

A DM-IM pattern may be defined within a PRB pair in a UE specificmanner. The DM-IM pattern for the UE may be defined as a function ofC-RNTI and a physical and/or virtual cell ID. A combination of C-RNTI,cell ID and/or virtual cell ID may be used as an initializationparameter for a sequence generation. The generated sequence may be usedas the DM-IM pattern. This may be applicable for the case ofquasi-orthogonal DM-IM patterns.

Furthermore, the DM-IM pattern may be a function of the frame numberand/or subframe number, and/or a PRB index. This may provide arandomization mechanism for intercell interference.

PDSCH Reception with DM-IMs

A DM-IM pattern in a PDSCH or E-PDSCH PRB pair allocated to a UE may bedefined, configured, or otherwise determined by the UE. Based on thisthe UE may measure interference from one or more of the DM-IMs that maybe present within the PRB pair. It may use the measurement(s) indemodulation, for example to suppress the interference. The UE may takeinto account the priorities of the DM-IMs and any other signal typeswhich may collide with the DM-IMs in the PRB pair. The UE may use thisto determine whether to include or exclude an RE in the interferencemeasurements.

A UE may receive an indication whether the DM-IMs may be present in aPRB to be decoded by the UE. This may be referred to herein as aDM-IM-ON-OFF indication. The DM-IM-ON-OFF indication may be provided tothe UE, e.g., by the eNB. It may be provided to the UE by higher layersignaling such as RRC or Medium Access Control (MAC) layer signaling, orvia physical layer signaling, such as in a DCI format. A DM-IM-ON-OFFindication may be included in a DCI format. This may provide a grant forthe PDSCH or E-PDSCH. A DM-IM may be included in the indicated pattern.

The ON or OFF indicated by a DM-IM-ON-OFF indication may apply to PDSCHallocations for the UE in or beginning with the next PDSCH allocation,or a future PDSCH allocation. For example, a DM-IM-ON-OFF received by aUE in a subframe n may indicate ON (e.g., DM-IMs may be present) or OFF(e.g., DM-IMs may not be present) in one or more of the following: PDSCHPRB pairs in subframe n, PDSCH PRB pairs beginning in subframe n, PDSCHPRB pairs in subframe n+k, for example n+4, or PDSCH PRB pairs beginningin subframe n+k, for example n+4.

In a given subframe in which PDSCH may be allocated to the UE, the UEmay take into account the DM-IM-ON-OFF indication applicable to thesubframe in determining whether DM-IMs may be present in PRB pairs ofits allocated PDSCH. If the applicable indication indicates a DM-IM isON, the UE may make and use DM-IM measurements as described herein. Ifthe applicable indication indicates the DM-IM may be OFF, or if the UEhas not received an indication that it may be ON, the UE may not makeand/or use the measurements.

In addition to, or instead of, including a DM-IM-ON-OFF indication inthe DCI format, an indication of which DM-IM pattern to use may beincluded in the DCI format. The pattern indication may itself be used toindicate ON or OFF, e.g., one value may mean OFF. Alternatively, the useof a DCI format, which may include the pattern indicator, may mean ON orOFF. The use of the one that does not include the indicator may meanOFF.

The DM-IM may be used for all or a subset of downlink transmissionmodes. If a dynamic indication for DM-IM may not be used, downlinktransmission modes defined in previous 3GPP releases (i.e.,Release-8/9/10/11) may use DM-IM for PDSCH demodulation. This may betrue because an additional bit field in its DCI format may not berequired. However, if a dynamic indication for DM-IM may be used, suchas for indication of a DM-IM pattern or a DM-IM-ON-OFF indication, a newdownlink transmission mode for NAIC may be defined.

In one possible example, a new downlink transmission mode (e.g., TM-11)may be defined for the enhanced decoding (or NAIC) scheme, with a newDCI format (e.g., DCI format 2E) and a bit field for DM-IM configurationand/or DM-IM-ON-OFF indication. For example, the bit field in the DCIformat may include the configuration of the DM-IM pattern which may beas described earlier herein.

In one possible example, the DM-IM pattern may be indicated in the DCIformat associated with PDSCH transmission in the subframe. If K DM-IMpatterns are available, e.g., for a cell, [log₂K] bits may be used inthe DCI format associated with PDSCH or E-PDSCH transmission. This mayindicate which DM-IM pattern may be used to demodulate the correspondingPDSCH. If a UE receives this indication, the UE may measure interferencein the RE locations which may be indicated in a DM-IM pattern. Themeasured interference information may be used for demodulation in thesubframe.

The enhanced decoding scheme may be supported with a limitedtransmission rank. For example, a normal transmission mode (e.g., TM-10)may support up to rank 8, according to the eNB antenna configuration.Moreover, the enhanced decoding scheme may support up to a lower rank,such as rank 1 or rank 2. Thus, the field describing antenna ports andrank in the new DCI format may have a reduced size, compared to otherDCI formats such as 2C or 2D.

One or more of the following may apply to the interference measurements.

If multiple PRB pairs are allocated for a UE, the UE may assume that theinterference level may be different from one PRB pair to another. Thus,the interference measurement should not be averaged across the PRB pairsallocated for the UE.

PRB bundling may be used for interference measurement. Thus, a UE mayassume that the interference may be the same within the PRB bundlingsize (where the bundling size may be larger than 1 PRB pair).Accordingly, a UE may average the interference over multiple PRB pairs.In the latter case, the multiple PRB pairs may be consecutive in thefrequency domain. In an example, the PRB bundling may be activated ordeactivated via higher layer signaling. In this case, the bundling sizemay be predefined as a number of consecutive PRBs. In another example,the PRB bundling may always be used in a specific transmission modesupporting NAIC.

PRB bundling may be used for interference measurement. Therefore, a UEmay assume that the interference may be the same within the PRB bundlingsize (where the bundling size may be larger than 1 PRB pair).Alternately, a UE may average the interference over multiple PRB pairs.In the latter case, the multiple PRB pairs may be consecutive in thefrequency domain. In an example, the PRB bundling may be activated ordeactivated via higher layer signaling. In this case, the bundling sizemay be predefined as a number of consecutive PRBs. In another example,the PRB bundling may be used in a specific transmission mode supportingNAIC.

If PRB bundling may be used for interference measurement, a subset ofPRB pairs within the bundled PRB pairs may contain only DM-IMs.Therefore, a UE may measure interference from the PRBs containing DM-IM,and use the interference information for other PRB pairs within bundledPRB pairs.

In one possible example, DM-IMs and/or the new downlink transmissionmode may be (e.g., may only be) used in a subset of subframes. One ormore of the following may apply.

A DCI format used for NAIC (e.g., DCI format 2E) which includes a bitfield for DM-IM configuration or an indication (e.g., DM-IM patternindex) may be (e.g., may only be) used in the subset of subframes whichmay contain DM-IMs.

The subset of subframes and/or radio frames supporting NAIC, or whichmay include DM-IMs, may be configured via higher layer signaling, theupper layer signaling may be dedicated signaling or broadcast signaling(e.g., MIB or SIB-x).

The subset of subframes supporting NAIC, or which may include DM-IMs,may be configured among the MBSFN subframes. A subset of the MBSFNsubframes may be used as NAIC subframes.

The subset of subframes supporting NAIC, or which may include DM-IMs,may be configured among the ABS subframes. A subset of the ABS subframesmay be used as NAIC subframes.

NAICS

In one possible example, the existence of co-scheduled UE informationmay be carried in a DCI format used for NAIC. For example, aco-scheduling indicator (or interference indicator) may be used toinform a UE whether there may be a co-scheduled UE. The indicator may beone bit.

The UE may estimate an IS by measuring DM-RS. The DM-RS may be used forthe IS. The estimate may be based on an indication of co-scheduledinterference and/or detection of energy level above a threshold. Thethreshold may be a predetermined threshold.

One or more of following may apply. In a given subframe with a PDSCHallocation for a certain UE, there may be a (e.g., at least one)co-scheduled UE, or co-scheduled interference. It (they) may beindicated by the co-scheduling indicator being activated (e.g.,indication bit=1). In this case the certain UE may perform energydetection of the antenna ports not allocated for the certain UE. If thecertain UE may determine that a specific antenna port has higher powerthan a threshold, the certain UE may consider that antenna port to havean interference signal and may try to suppress the interference.

In a given subframe with a PDSCH allocation for a certain UE, there maybe a (e.g., at least one) co-scheduled UE, or co-scheduled interference,which may be indicated by the co-scheduling indicator being activated(e.g., indication bit=1). In this case the certain UE may perform energydetection of the antenna ports not allocated for the certain UE. If thecertain UE may determine that a specific antenna port has higher powerthan a threshold, the certain UE may consider that antenna port to havean interference signal and may try to suppress the interference.

In a given subframe with a PDSCH allocation for a certain UE, there maynot be any co-scheduled UE, or co-scheduled interference, which may beindicated by the co-scheduling indicator being deactivated (e.g.,indication bit=0) or not being present. In this case, the certain UE mayskip performing energy detection of the antenna ports not allocated forthe certain UE. In order to allow energy detection based interferenceblind detection, orthogonal reference signals (antenna ports) may be (ormay need to be) used for the transmission mode for NAIC.

If there may be a co-scheduled UE (e.g., at least one) or co-scheduledinterference, and/or if the co-scheduling indicator may be activated, RElocations (e.g., all RE locations) for two CDM groups of DM-RS ports7-14 may be reserved. The RE locations for the two CDM groups may berate matched around, or punctured for, PDSCH transmission. There may notbe any co-scheduled UE or co-scheduled interference, and/or theco-scheduling indicator may be deactivated. In this case the CDM group(e.g., only the CDM group) containing the DM-RS port used for PDSCHtransmission may be rate matched around, or punctured for, PDSCHtransmission. Based on knowledge of whether there is any co-scheduling,the UE may account for the corresponding rate matching or puncturingwhen decoding the PDSCH. Knowledge of whether there is any co-schedulingmay be indicated by the co-scheduling indicator. The DM-RS port and theantenna port may be used interchangeably.

For example, FIG. 3 shows a schematic representation of a pattern 300including RE locations for two CDM groups, CDM group 1 and CDM group 2of DM-RS ports 7-14. The CDM group 1, indicated as Cs in pattern 300,contains DM-RS ports {7, 8, 11, 13}. The CDM group 2, represented as Dsin pattern 300, may contain DM-RS ports {9, 10, 12, 14}. As an example,DM-RS port 7 may be used for PDSCH transmission, and the co-schedulingindicator may be activated. Under these circumstances the RE locationsfor both CDM groups 1 and 2 may be rate matched around, or puncturedfor, PDSCH transmission and reception. Moreover, the RE locations forthe CDM group 1 may be rate matched around, or punctured for, PDSCHtransmission and reception if the co-scheduling indicator may bedeactivated. When both CDM groups are rate matched around or punctured,the UE may perform energy detection on the CDM group 2 antenna ports.The energy may be used to determine if there may be interference.

If there may be a (e.g., at least one) co-scheduled UE or co-scheduledinterference and/or if the co-scheduling indicator may be activated, aUE may assume that there may be co-channel interference in the same CDMgroup in which the DM-RS port for the UE may be located. The UE mayperform energy detection for the DM-RS ports located in the same (e.g.,only in the same) CDM group.

There may be a (e.g., at least one) co-scheduled UE or co-scheduledinterference, and/or if the co-scheduling indicator may be activated.Under these circumstances a UE may assume that there may be co-channelinterference in the same CDM group in which the DM-RS port for the UEmay be located. The UE may perform energy detection for the DM-RS portslocated in the same (e.g., only in the same) CDM group.

There may be a (e.g., at least one) co-scheduled UE or co-scheduledinterference, and/or the co-scheduling indicator may activated. Underthese circumstances, the DM-RS Scrambling ID (SCID) may set to apredefined value such as 0 or 1.

In another possible example, the information regarding the existence ofone or more co-scheduled UEs, and the number of co-scheduled UEs (and/orlayers), may be carried in a DCI format. For example, the DCI format maybe a DCI format used for an enhanced decoding scheme. A UE may beinformed of the number of interfering antenna ports and/or otherco-scheduling information. One or more of following may apply. Thenumber of interfering antenna ports may be indicated within a full setor a restricted set, such as {1, 2, 3, 4}. For a restricted set case, ann-bit (e.g., 2-bit) indicator may be used to inform the UE of the numberof interfering antenna ports. If a restricted set is used, higher layersignaling may configure the subset. For example, a transmission modewhich is not used for the enhanced decoding scheme may support up to a 8layer transmission. The full set may indicate 7 layers. Thus, the numberof interfering antenna ports may be one of {1, 2, 3, 4, 5, 6, 7}.Moreover, the restricted set may indicate a subset of the number ofinterfering antenna ports such as {1, 2}. A 4 layer example 302 may beshown in pattern 300.

The restricted set may be useful for reducing the control signalingoverhead. In this case eNB may not schedule more than two interferingantenna ports.

Use of Modulation Scheme

A real-valued modulation may be used in order to increase theinterference rejection capabilities at a UE receiver. The MMSE-IRC andWL-MMSE-IRC receivers may perform better as the degrees of freedomincrease at the UE receiver. Additionally, real-valued modulation maydouble the degrees of freedom, since the two orthogonal domains, namelyreal and imaginary, may be further exploited to reject interference.M-ary Pulse Amplitude Modulation (PAM), as an example but withoutlimitation to any type of modulation, may be used as a real-valuedmodulation. In order to keep the same spectral efficiency, eachcomplex-valued modulation scheme may have a corresponding real-valuedmodulation scheme.

Referring now to FIG. 4 , there is shown a table 400 setting forth acomplex-valued modulation scheme, and a real-valued modulation scheme,according to a modulation order and/or a bit width. Thus, thecomplex-valued modulation 402, the real-baled modulation 404, and themodulation order Q_(m) 406 may be shown for four cases in table 400. Thefour cases may include the single bit case 408 [b(i)], the pairs of bitscase 410 [b(i), b(i+1)], quadruplets of bits case 412 [b(i), b(i+1),b(i+2), b(i+3)] and hextuplets of bits case 414 [b(i), b(i+1), b(i+2),b(i+3), b(i+4, b(i+5)].

Referring now to FIG. 5 , there is shown a schematic representation 500of an M-ary PAM, for the M=2 case 502 and the M=4 case 504. The PAM ofrepresentation 500 may be defined in, for example, only the real domain.The distances between any two adjacent constellations may be the same ina specific M-ary PAM.

The UE may determine the type of modulation scheme used from aconfigured mode of operation, or from operation, or from the value of afield in the received DCI. In one possible example, a different set ofmodulation schemes may be used for downlink transmission according to amode of operation. The downlink transmission may include physicalchannels such as PDSCH, (E)PDCCH, PBCH or a new channel (e.g., E-PDSCH).In one of these cases, one or more of following may apply.

Two modes of operation may be defined, for example a normal mode and anenhanced decoding (or NAIC) mode. The names of the modes may be definedin any way. For the two modes of operation, at least one of followingsmay apply.

A UE may be configured with a mode of operation by higher layersignaling or informed via a broadcasting channel. In another example, adynamic indication may be used to indicate whether a UE may perform in anormal mode or an NAIC mode. Alternatively, a subset of physicalresources including subframe, radio frame, and/or PRBs may be configuredfor use as a specific mode of operation.

A mode of operation may be predefined according to the physicalresources, for example UE-ID, cell-ID and/or a specific systemparameter. For instance, a subset of subframes, radio frames, and/orPRBs may be predefined for use in an NAIC mode of operation.Additionally, any other subframes, radio frames, and/or PRBs may be usedas the normal mode of operation. A UE may receive a downlinktransmission in the physical resources, which is predefined to be usedas an enhanced decoding mode of operation. Under these circumstances,the UE may receive the downlink transmission with an enhanced decodingmode. In another example, a subset of C-RNTI may be reserved for theenhanced decoding mode operation. Furthermore, if a UE may be configuredwith a C-RNTI in the subset, the UE may receive downlink transmissionwith enhanced decoding mode of operation.

Other modes of operation may be used for a subset of downlinktransmissions. In an example, the NAIC mode of operation may only beapplicable for PDSCH and EPDCCH. Thus, the modes of operation may beused only for PDSCH and EPDCCH. The normal mode of operation may be usedfor another downlink transmission. In another example, the NAIC mode ofoperation may be used only for the PDSCH.

In the normal mode of operation, a UE may assume that the modulationschemes for all or a subset of downlink transmissions may be based on acomplex-valued modulation scheme. For example, it may be one of BPSK,QPSK, 16QAM, and 64QAM. A MCS level may be explicitly indicated for aspecific downlink transmission such as PDSCH. Thus, a UE may assume thecomplex-valued modulation corresponding to the MCS level fordemodulation.

In the enhanced mode of operation, a UE may assume that the modulationschemes for all or a subset of downlink transmissions may be based on areal-valued modulation scheme. If a MCS level may be explicitlyindicated for a specific downlink transmission, such as PDSCH, a UE mayassume the real-valued modulation corresponding to the MCS level fordemodulation.

The enhanced decoding or NAIC mode may be defined as a downlinktransmission mode (e.g. TM-11). Additionally, the real-valued modulationmay be used for the NAIC mode only. Therefore, if a UE may be configuredwith NAIC mode, the modulation scheme for each modulation order in a MCStable may be based on a real-valued modulation.

The transmission mode used for NAIC may be the same as a specificdownlink transmission mode using complex-valued modulation. An exceptionmay be for using real-value modulation. The transmission mode used forNAIC may support rank-1 transmission.

In another possible example, complex valued modulation and real-valuedmodulation may be mixed. Furthermore, both modulations may be a part ofa MCS table. Thus, an eNB scheduler may select any of modulation schemesdynamically. It may indicate an MCS level in DCI format. In this case,one or more of following may apply.

The MCS table size may double so that complex-valued modulation may beused for an MCS index 0 to 31. Additionally, real-valued modulation, forexample, may be used for the MCS index 32 to 63. Therefore, a 5 bit MCSfield in a DCI format may be increased to a 6 bit MCS field.

In an MCS table, the real-valued modulation may be introduced for aspecific modulation order. For instance, 4-ary PAM may be introduced forthe modulation order 2 (Qm=2) in the MCS table. The specific modulationorder may be replaced with real-valued modulation.

In an MCS table, for each modulation order, a subset of MCS indexes maybe replaced with real-valued modulation. For example, if an MCS index0˜9 is used for modulation order 2 with QPSK, a subset of MCS index 0˜9(e.g., MCS index 0˜3) may be replaced with 4-ary PAM modulation. Theremaining MCS index 4˜9 may continue to use Quadrature Phase ShiftKeying (QPSK) modulation.

Determining IS Information

Possible examples that a UE may employ for determining the ISinformation that is used in an enhanced decoding scheme may bedescribed. The UE may use the IS information in different ways toimprove the probability of success of decoding its desired information.In some examples, the UE may utilize a limited amount of IS informationto estimate the IS in the decoding process. For example, it may use theRB assignment and the modulation order. In other examples, the UE mayfully decode the IS (at the bit level) to completely remove itscontribution to the total received signal.

General Examples

In some possible examples, without limitation, the UE may extract ISinformation through post processing at the receiver. This may be donewithout any network assistance (blind estimation). The extracted ISinformation may include the modulation order of the interferer, forexample BPSK, QPSK, QAM16, QAM64, etc. Additionally it may include theTransmission Mode (TM) of the interferer, for example Transmit Diversity(TM2), Open-Loop Spatial Multiplexing (TM3), Closed-Loop SpatialMultiplexing (TM4), etc. It may also include the transmission power ofthe interferer, for example the ratio of PDSCH Energy Per ResourceElement (EPRE) to a cell-specific reference symbol EPRE.

In some possible examples, the UE may obtain IS information using apriori knowledge regarding the IS. For instance, in the case where theIS includes transmissions over physical channels such as E-PDCCH, PDCCH,PCFICH, PHICH or PBCH, the UE may determine the following parameters. Itmay determine the precoding at the transmitter, for example, it maydetermine space-frequency block coding may be the baseline transmitdiversity for PDCCH, PCFICH, PHICH & PBCH. It may also determine thetransport block size. For example it may determine the total number ofcoded bits transmitted on PBCH in a single subframe may be fixed at 480.Additionally, the UE may also determine the modulation order, forexample the modulation order for control channels may be QPSK. AUE-specific RS scrambling index associated with EPDCCH may also bedetermined. For example, n_(SCID) ^(EPDCCH) for EPDCCH may be fixed andmay be equal to 2. UE specific RS antenna ports associated with EPDCCHmay also be determined. For example, n_(SCID) ^(EPDCCH) for EPDCCH maybe fixed and may be equal to 2.

In some examples, the UE may obtain explicit IS information throughphysical or higher layer signaling from the network. For instance, atleast one of the following parameters may be indicated for an IS: MCSassigned to the interferer, transport block size(s) of the interferingdata packet, spatial a precoder used at the transmitter for theinterferer, for example the Precoder Matrix Indication (PMI) index inTM2, TM3 and TM4 for LTE systems, the actual RB assignment of theinterferer, the transmission Rank of the signal intended for theinterferer, the transmission Mode of the interferer, the UE-specific RSscrambling index of the interferer, the identity of the interfering UE,and/or the C-RNTI.

Configuration of IS Information for Multiple Potential ISs

In a dynamic DL traffic environment, an eNB may not have drasticscheduling limitations imposed on it. For example, an eNB may servemultiple UEs, each with DL data at similar times. In such a scenario,the scheduler may be able to determine the UEs that may be scheduledwith specific resources based on metrics. This may ensure the optimalquality of service and/or throughput that may be achieved for the UEs.When used in combination with frequency selective scheduling, an eNB maydynamically determine whether the UEs should be paired for Multi UserMIMO (MU-MIMO). It may also determine which UEs may be paired.Furthermore, in some deployments, it may be possible for a cell to beinformed of other UEs scheduled in specific resources. However, a cellmay not have control over such scheduling.

To achieve such scheduling flexibility, a UE may be expected to canceland/or suppress interference from at least one of potentially multipleIS. At any time, a UE may expect to cancel and/or suppress possibly asingle (or possibly a few) IS. However, the IS may change dynamicallyover different subframes, It may potentially also change over differentPRB resources in the same subframe.

To enable a UE to be able to cancel and/or suppress interference fromdifferent IS, a UE may be pre-configured, via higher layers (e.g., RRCsignaling), with a list of possible IS, as well as necessary parameters.Such a configuration may include a list of potential IS, as well as anIS index. Furthermore, for a different IS, the UE may be preconfiguredwith parameters that may correspond to parameters semi-staticallyconfigured for another UE for which the IS may be destined. Forinstance, such parameters may include (assuming the IS corresponds to aPDSCH transmission in TM10 for another UE) at least one of thefollowing.

The parameters may include PDSCH RE mapping and quasi-co-location. Thismay be a list of values for a ‘PDSCH RE Mapping and Quasi-Co-LocationIndicator’ field. It may also be a parameter set for each value. Aparameter set for these values may include: crs-PortsCount-r11 (orcrs-PortsCount-r12) and or crs-FreqShift-r11 (or crs-FreqShift-r11).This may be used to indicate where a UE assigned the IS assumes CRS andtherefore may have no transmission of data. It may includembsfn-SubframeConfigList-r11 (or mbsfn-SubframeConfig-r12). This may beused to indicate the subframes in which a UE that is assigned the IS mayassume a Multicast-Broadcast Single-Frequency Network (MBSFN). Theparameter set for these values may also include: csi-RS-ConfigZPId-r11(or csi-RS-ConfigZPId-r12). This may be used to indicate the resourceswhere a UE that receives the IS assumes ZP CSI-RS. It may thereforeassume no transmission of data. It may also include pdsch-Start-r11 (orpdsch-Start-r12). This may be used to indicate the OFDM symbol where aUE assigned the IS assumes data transmission may begin. It may alsoinclude qcl-CSI-RS-configNZPId-r11 (or qcl-CSI-RS-ConfigNZPId-r12). Thismay be used to indicate the CSI-RS resource that may be quasi co-locatedwith PDSCH antenna ports where a UE assigned with the IS would expecttransmission.

The parameters which may be semi-statically configured for another UEfor which the IS may be destined may also include the possible values ofn_(ID) ^(DMRS,i). They may also include the mapping of n to n_(SCID)^(DMRS,i) and/or search spaces that may be used for the DCI of the IS.The search spaces may include UE-specific search spaces. They may alsoinclude common search spaces. The search spaces may be for PDCCH and/orEPDCCH. The parameters may also include EPDCCH configurations for one ormore of the IS. They may also include an RNTI value to be used whendecoding the PDSCH of the IS. It may also include any other ZP and/orNZP CSI-RS configuration that a UE assigned with the IS may assumecontains no transmission of data.

In addition, a number of parameters may be provided for each IS. Forexample, without limitation, a set of subframes may be provided wherethe UE may expect an IS to potentially be present. Additionally, a setof PMIs that may be used for the transmission of such an IS may beprovided.

The UE May Obtain IS Information by Decoding a DCI Containing the DLAssignment Corresponding to the IS

The IS index may be used by the network to dynamically indicate to a UEwhat IS (if any) a UE may assume for proper interference cancellingand/or suppressing. For example, in a DCI assigning DL data for a UE, anew field (for example, 3 bits or any other number of bits) may indicateto the UE the IS index of an IS. One code point may correspond to theabsence of any IS. Based on the presence and/or the value of such an ISindex, a UE may decode the DCI of such an IS to determine theappropriate DL assignment of the IS. This may be done by using theparameters pre-configured with the IS index. The presence and/or thevalue of such an IS index may also enable the UE to perform interferencecancellation and/or suppression.

In another example, a UE may not be pre-configured with the parametersof the DCI of each IS. Instead, in this example, each DCI may alsoinclude a bit field indicating what IS index it may be intended for.Therefore, a UE may blindly decode all appropriate DCIs until itsuccessfully determines the DL assignment for the IS that it isindicated in its own DCI.

In another example, each IS may also be tied to some parameters of theDL transmission for the UE. For example, if a UE receives DCI in aspecific search space, it may assume that a specific IS may be presentduring that transmission. A possible parameter that may implicitlyinform a UE which IS to consider may include one of more of thefollowing. It may include a search space used for the DL assignment forthe UE. It may also include specific parameters of the DL assignment,such as MCS, PMI, DM-RS ports, Virtual Cell Identity (VCID), PDSCH REMapping and/or Quasi-Co-Location Indicator field. It may include the useof PDCCH or EPDCCH. A parameter of the EPDCCH transmission may beincluded. Additionally, the timing of the DL assignment (e.g., thesubframe) may be included.

There may also be an IS index that indicates to a UE that it shouldexpect high interference. Or, there may be a flag in the DCI of the DLassignment for the UE. However, the interference may not be from one ofthe pre-configured IS. There may also be an IS index that that mayindicate to a UE that it should not expect interference from anypre-configured IS. Or, there may be a flag in the DCI of the DLassignment for the UE. Alternately, it may indicate that Single UserMIMO (SU-MIMO) transmission may occur in the subframe.

A UE capable of handling interference may blindly detect its own DLassignments. It may also blindly detect those corresponding to the IS ona given subframe. In order to reduce the complexity of blind decodingattempts, the UE may employ one or a combination of all or some of thefollowing schemes.

The UE may attempt to search for its own DL assignment and those of theIS on the same set of Evolved Control Channel Elements/Control ChannelElements (ECCEs/CCEs). The UE may be expected to monitor for DLassignments. The set of candidate control channels formed by ECCEs/CCEsmay also be known as a search space in LTE systems. Accordingly, in someor all of the subframes, the UE may attempt to simultaneously decodemultiple EPDCCHs/PDCCHs in the UE-specific search space at eachaggregation level. If the detected CRC of the DCI message checks usingthe identity of the interferer, the UE may declare that the interferer'sDL assignment may be successfully decoded. This may be done using theRNTI and/or other parameters of the interferer.

The UE may attempt to blindly detect the DL assignments intended forinterferers in a different search space than its own UE-specific searchspace. According to this scheme, the UE may first identify the searchspace of the interfering UE, for example, using the informationregarding the identity of the interferer provided by the network and/orthe subframe number. It may also attempt to search for EPDCCH/PDCCHintended for the interferer. It may also check the corresponding CRCagainst the identity of the interferer.

The search spaces for the victim UE and any interferers may partiallyoverlap. This may limit the number of blind decoding attempts at the UE.Alternatively, the number of ECCEs/CCEs candidates and/or aggregationlevels in the search spaces for which the UE may be expected to monitorfor DL assignments intended for the interferer(s) may be restricted bythe network. Thus, the UE may conduct fewer blind decoding attempts onother search spaces possibly containing the DL assignments for theinterferer(s) than that of its own. This may be accomplished bysearching on a subset of ECCEs/CCEs candidates in each search space.

The UE May Obtain the Location of the DCI Containing the Assignment ofthe IS from an Explicit Indication Contained in the DCI Containing itsOwn Assignment

In one possible example, the UE may be explicitly indicated the enhancedcontrol channel elements (ECCE's). This may be where the DL assignmentof the IS may be found. This method may further relieve processingrequirements. For instance, the UE may be explicitly indicated at atleast one of a starting ECCE index, and/or an aggregation level, toreduce the number of possible candidates. This may reduce the number ofpossible candidates to a single candidate. This indication may becontained in the DCI containing the assignment for the UE. Alternately,it may be contained in another DCI containing NAICS information. TheNAICS information may be decoded in the same or in a previous subframe.

In a case of EPDCCH monitoring, the UE may be configured with twoEPDCCH-PRB-sets. The UE may monitor the sets. These may include EPDCCHcandidates corresponding to their own DL assignment on the firstEPDCCH-PRB-set. They may also include the EPDCCH candidates. The EPDCCHcandidates may be intended for the interferer on the secondEPDCCH-PRB-set. Moreover, each EPDCCH-PRB-set may be configured foreither localized or distributed EPDCCH transmission. For example, fromthe UE's perspective it may be beneficial that the UE receive its ownEPDCCH on the EPDCCH-PRB-set configured for localized EPDCCHtransmission. It may also be beneficial that the UE receive the EPDCCHof the interferer on the EPDCCH-PRB-set configured for distributedtransmission. This approach may further improve the EPDCCH detectionperformance at the UE's receiver. This may be the case, for example, ifno beamforming is applied on the interferer's EPDCCH transmission.

For a UE configured for EPDCCH monitoring, the UE may explicitly receiveone or a combination of the following parameters. The parameters maycorrespond to the interferer's EPDCCH configuration from the network.The parameters can include, without limitation, the number ofEPDCCH-PRB-sets, the number of PRB pairs constituting eachEPDCCH-PRB-set, the PRB pairs corresponding to each EPDCCH-PRB-set, theEPDCCH transmission mode for each EPDCCH-PRB-set (distributed orlocalized), the EPDCCH starting position, and/or the EPDCCH Format, orEPDCCH ID for each EPDCCH-PRB-set i, i.e., n_(ID,i) ^(EPDCCH) fori∈{0,1}.

Furthermore, the UE may implicitly derive the information related to theinterferer's EPDCCH configuration. It may use a mathematical formula.The mathematical formula may be a function of the UE's EPDCCHconfiguration. For example, for each EPDCCH-PRB-set, the UE may derive acombinatorial index r′. The index r′ may correspond to the PRB indicesconstituting EPDCCH-PRB-set of the interferer. The derivation may beperformed by applying an offset to the configured parameterresourceBlockAssignment-r11. The configured parameterresourceBlockAssignment-r11 may indicate a combinatorial index rcorresponding to the PRB indices constituting an EPDCCH-PRB-set of itsown. According to another example, the UE may derive the number ofEPDCCH-PRB-sets. Additionally, the UE may derive the number ofEPDCCH-PRB sets. It may derive the number of PRB pairs corresponding toeach EPDCCH-PRB-set of the interferer. The number of PRB pairs may bederived according to some predetermined values. With regard to an EPDCCHstarting position of the intra-cell interferer, the UE may assume thatthis parameter may be the same as its own.

For a UE configured to monitor EPDCCH, for each EPDCCH-PRB-set, the UEmay use the parameter set indicated by the higher layer parameterre-Mapping QCLConfigListId-r11 for determining the EPDCCH RE mapping andEPDCCH antenna port quasi co-location of the intra-cell interferer(s).

In the case of inter-cell interference mitigation and/or cancellation,the UE may explicitly receive, for example, one, or a combination ofsome of, or all of, the following parameters from the network. It mayexplicitly receive the number of CRS antenna ports for PDSCH RE mapping.It may explicitly receive the CRS frequency shift for PDSCH RE mapping.It may explicitly receive the MBSFN subframe configuration for PDSCH REmapping. It may explicitly receive the zero-power CSI-RS resourceconfiguration(s) for PDSCH RE mapping. It may explicitly receive thePDSCH starting position for PDSCH RE mapping. It may explicitly receivethe CSI-RS resource configuration identity for PDSCH RE mapping. Theseparameters may be received for determining the EPDCCH RE mapping and/orthe EPDCCH antenna port quasi co-location corresponding to theinter-cell interferer(s).

In one possible example, a NAICS capable UE may obtain IS informationfor at least one interfering UE by means of a common DL signalingmessage. It may use a group C-RNTI to identify the DL signaling messageas carrying information for the purpose of NAICS. For example, thecommon DL signaling message carrying information for the purpose ofNAICS may be sent as DCI on a DL common control channel such as PDCCH orEPDCCH.

By way of another example, a group C-RNTI assigned to the common DLsignaling message may carry information for the purpose of NAICS. It mayserve to decode the signaling message. It may be signaled from thenetwork to one or more UEs. For example, a NAICS capable UE may beassigned one or more group C-RNTI used to identify DL signaling messagescarrying information for the purpose of NAICS. The number of such groupC-RNTIs to be decoded may be subject to configuration by the network. Itmay also be subject to UE capabilities. If a UE signals that it may becapable of supporting simultaneous decoding for up to 2 interferers, thenetwork may choose to configure the NAICS capable handset to decode for1 or for 2 interferers.

A UE that has a group C-RNTI may attempt to decode a corresponding DLcontrol channel. It may decode for the possible presence of the DLsignaling message. The DL signaling message may be in subframes thatwere determined to be candidates for NAICS. Depending on UE capabilitiesand system configuration, these subframes or transmission time intervalsmay include all or only a subset of them. Relevant subframes ortransmission time interval candidates for decoding of the DL signalingmessage by a NAICS capable UE may alternatively, or in conjunction, bederived by a UE. They may be derived through a rule that does notrequire decoding for the presence of the DL signaling message in allsubframes.

The later approach may be particularly advantageous. It may reduce theneed for a NAICS capable UE to determine the presence of interferers.This may be useful in cases where subframes offer only limitedflexibility in terms of sending scheduling information. It may also beuseful where PDSCH allocations are limited. For example, it may beuseful in LTE TDD special subframe configurations.

In one possible example, a NAICS capable UE may decode a DL signalingmessage containing IS information. It may perform the decoding insubframes or transmission time intervals subject to the condition thatit may be actually scheduled DL data.

For example, a NAICS capable UE may attempt to decode for the presenceof PDSCH DL assignment messages on a DL common control channel, such asPDCCH or EPDCCH. In these channels the DL assignment message may containscheduling information for the UE under consideration. If the UE hasdetermined that it has DL data on PDSCH scheduled by the network in thesubframe or transmission time interval, it may then attempt to decode aDL signaling message carrying information for the purpose of NAICS.

The later approach may be particularly advantageous if a NAICS capableUE may only decode scheduling information for an interferer on an asneeded basis. This may reduce decoding complexity for a NAICS capableUE. This may reduce the complexity. It may avoid the decoding ofinformation about interferers in subframes when the UE underconsideration determines there may be no DL data to be received.

Different implementations for the above described approach may bepossible. For example, a NAICS capable UE may first and/or exclusivelydecode a PDCCH or EPDCCH for the presence of a first DL assignmentmessage. The first DL announcement message may announce its DL data onPDSCH using its assigned unicast C-RNTI. It may proceed decoding for thepresence of a second DL signaling message with the group C-RNTI forNAICS purposes if the first DL assignment message is found. In anotherembodiment, the NAICS capable handset may decode the PDCCH or EPDCCH forthe presence of either the first or the second DL messagesimultaneously. However, the UE receiver for processing of the PDSCH maythen be configured as a function of the resulting decoding result. If DLdata is not determined to be present, any possibly decoded second DLsignaling message for NAICS purposes may be discarded. If DL data may bepresent in that subframe the NAICS capable handset may take theinformation obtained from the second DL signaling message into accountfor configuring the receiver. Whether the DL data is present may bedetermined from reception of the first DL assignment message,

The UE May Obtain IS Information, Such as the Identity of an IS, from aDCI Encoded in a PDCCH or E-PDCCH Separate from Its Own Assignment

In one possible example, a NAICS capable UE may obtain IS informationfor at least one interfering UE by means of a sequential decodingprocedure.

In one step, a NAICS capable UE may determine the presence of at leastone interferer. It may make the determination by decoding a first DLsignaling message containing NAICS information. In another step, the UEmay use the information obtained through the DL signaling message toderive IS information for the interfering UE. The NAICS capable UE mayalso demodulate and decode its PDSCH in the subframe or transmissiontime interval. This may be done by taking into account the assistanceinformation obtained in the foregoing steps.

In one example technical realization, and as one exemplary embodiment,the network may configure a group of M NAICS capable UEs. The UEs maydecode for the presence of a common DL signaling message on PDCCH orEPDCCH. It may do this by using a group RNTI, e.g., NAICS RNTI. The MNAICS capable UEs may be configured by the network with a list of N₁,N₂, N_(M) C-RNTI's. The list of C-RNTI's for a UE may correspond to aset of N possibly interfering UEs. A UE under consideration may bescheduled for DL data on PDSCH in a given subframe or transmission timeinterval. In one step, in the subframes, the base station may schedulesome L UEs for DL data. Correspondingly it may issue a number L of DLassignment messages for the scheduled UEs on PDCCH or EPDCCH. The basestation may schedule both legacy UEs and UEs that support NAICS. Inaddition, the base station may send the NAICS DL signaling message usingthe NAICS group C-RNTI. The NAICS DL signaling message may contain alist of sequential indices for the NAICS capable UEs to identify theirstrongest interference. For example, the NAICS capable UEs may beconfigured with 4 C-RNTI's of candidate interfering UEs. The payload ofthe NAICS DL signaling message may be a concatenation of 2 bit indexvalues pointing to these. For example, the first 2 bits in the messagemay identify the strongest interferer for the first NAICS capable UE.The next 2 bits may identify the strongest interferer for the secondNAICS capable UE, and so on. A NAICS capable UE may decode the PDCCH orEPDCCH. If the NAICS DL signaling message may be decoded using the NAICSgroup C-RNTI, it may use its corresponding index value. It may use theindex value to obtain the actual C-RNTI of the UE from its networkconfigured list. In a further step, once the NAICS capable UE obtainsthe actual C-RNTI for the interfering UE, it may decode DL schedulinginformation on PDCCH or EPDCCH for that UE.

This approach may be advantageous in that any NAICS capable device maydecode only for one additional DCI, i.e., the NAICS signaling message,in subframes where it may be scheduled DL data. Moreover, when thenetwork configures the M NAICS capable UEs with a list of N₁, N₂, . . ., N_(M) C-RNTIs, respectively, there may be no limitation of schedulingflexibility. This may mean that a NAICS capable UE only decodes a singleDL signaling message. This may allow it to derive the identity of aninterferer. As a consequence, the UE complexity necessary to supportNAICS may be kept low. Furthermore, full flexibility and throughputgains due to scheduling may be possible. In addition, legacy UEs may bescheduled as before. For example, the legacy UEs may be allocatedanywhere. NAIC capable handsets may be able to attempt IC/IS in the sameway as for newer equipment.

Based on an approach described herein, alternative realizations may beenvisioned. For example, NAICS capable UEs may be split into differentgroups, and they may be assigned to monitor and decode different NAICSDL assignment messages. Both the strongest and second strongestinterferers may be identified for a NAICS capable UE. The interferersmay be identified through the NAICS DL signaling message. Additionally,the DL signaling message may contain index values for the monitoring UEsthat have DL data. The DL data may be scheduled in the subframe ortransmission time interval under consideration. Furthermore, the NAICSDL signaling message may contain other information to aid the decodingUE derive scheduling information for a subframe.

Physical Layer Procedures with Enhanced Decoding Scheme

Conditions for Use of IS Information in a Subframe

A UE May Use an Enhanced Decoding Scheme for Decoding a DL Channel in aSubframe if Certain Conditions May Be Met, Such as Receiving anIndication in DCI

A UE may attempt to decode on a DL physical channel using an enhanceddecoding scheme in a specific subframe if at least one of a subset ofconditions is met. If at least one of the conditions is not met the UEmay attempt decoding using a legacy decoding scheme.

The enhanced decoding scheme may involve decoding DL information usingat least one of: IS information to cancel or suppress interference, anew modulation scheme (e.g. real-valued modulation), a real-valuedmodulation scheme or another scheme facilitating removal ofinterference, and/or an interference measurement such as DM-IM fordemodulation purposes.

A subset of conditions may be taken from at least one of the following.The UE may be configured to use a transmission mode in which an enhanceddecoding scheme may be used for the DL physical channel. This may be anewly defined transmission mode (e.g. TM-11), and/or an enhanceddecoding or NAIC mode. Another condition in the subset of conditions maythe condition where the subframe for which the decoding takes place ispart of a semi-statically configured subset of subframes. An enhanceddecoding scheme may be used in the subframes. Additionally, the UE maybe configured with IS information applicable to the subframe accordingto a semi-static configuration. Further conditions may include a casewhere the subframe for which the decoding takes place is a certain typeof subframe. For example, the UE may use the enhanced decoding scheme innormal subframes and/or in MBSFN subframes.

Another condition may be a case wherein a physical RB in which thedesired signal is decoded is a subset of, or overlaps with, a set ofsemi-statically configured physical RBs. Enhanced decoding may be usedfor the set of semi-statically configured physical RBs. In another case,a UE may receive DCI applicable to the reception of the DL channel inthe subframe, for instance a DL assignment in E-PDCCH. This may containan indication that an enhanced decoding scheme can be used or not used.This may also be a condition in the subset of conditions. For instance,the DCI may contain an IS information field, for which a code pointindicates that no IS information should be used.

Other conditions may include a case wherein a UE may decode at least oneE-PDCCH or PDCCH. The E-PDCCH or PDCCH may contain IS informationapplicable to the subframe. The information may be received in the sameor a previous subframe. For instance, the UE may use IS information froman E-PDCCH containing a DL assignment for a C-RNTI other than its own(e.g., for another UE), if configured to gain IS information fromassignments intended for the C-RNTI. This may possibly apply even if theUE does not receive DCI for its own assignment in the subframe. Anexample of this may be the case of an SPS assignment. The IS informationreceived in a subframe may indicate that IS information received in aprevious subframe is not applicable. For instance, the UE may decode anE-PDCCH containing a dynamic assignment for another C-RNTI that mayoverride a previously received SPS assignment for the subframe.

A subframe for which decoding takes place may be a certain type ofsubframe. For example, it may be a type of subframe wherein the UE mayuse only an enhanced decoding scheme in normal subframes. It may useonly an enhanced decoding scheme in MBSFN subframes.

Additionally, the physical RBs in which the desired signal is decodedmay be a subset, or overlap with, a set of semi-statically configuredphysical RBs for which enhanced decoding it to be used.

In another such condition the UE may have received DCI applicable to thereception of the DL channel in the subframe (for instance, a DLassignment in E-PDCCH) containing an indication that an enhanceddecoding scheme may be used or not used. For instance, the DCI maycontain an IS information field, for which one of the code pointsindicates that no IS information should be used.

In another such condition, a UE may have decoded at least one E-PDCCH orPDCCH containing IS information applicable to the subframe (which may bereceived in same or previous subframe). For instance, the UE may use ISinformation from an E-PDCCH containing a DL assignment for anotherC-RNTI than its own (e.g., for another UE). The IS information may beused if the UE is configured to gain IS information from assignmentsintended for this C-RNTI. Possibly, this may apply even if the UE doesnot receive DCI for its own assignment in this subframe, such as in caseof a Semi-Persistent Scheduling (SPS) assignment.

The IS information received in a subframe may indicate that ISinformation received in a previous subframe may not be applicable. Forinstance, the UE may decode an E-PDCCH containing a dynamic assignmentfor another C-RNTI that may override a previously received SPSassignment for this subframe.

Provision of HARQ Feedback

In one example, a UE may provide HARQ feedback pertaining to a DLassignment in a subframe wherein the timing may depend on a condition.The condition may be whether IS information is used or configured to bepotentially used, in the subframe in which the DL assignment may bereceived, or (ii) whether the UE is configured to operate using ISinformation.

The use of IS information in decoding PDSCH assignments may increase theprocessing requirements at the receiver. To relax peak processingrequirements, and thus hardware complexity, it may be beneficial toincrease the latency between the reception of PDSCH and the transmissionof HARQ feedback pertaining to the PDSCH.

In one example, the latency of HARQ feedback may be semi-staticallyconfigured. It may be independent of whether IS information is used in aparticular subframe. For instance, in the case of an FDD modulationscheme, HARQ feedback may be provided in subframe n+n0 (where n0 may be,e.g., 5 or 6). This may occur when the UE may be semi-staticallyconfigured to operate according to a certain transmission mode for whichIS information may be used, in a case of a TDD modulation scheme. HARQfeedback may be provided in subframe n+n0 where n0 would depend on thesubframe index n and the subframe configuration. However, it may be thesame or different (e.g. larger) than the corresponding value used in acase where another transmission mode (not using IS information) may beconfigured.

In another example, the latency of HARQ feedback may depend on whetherIS information is configured to be potentially used in a specificsubframe according to a semi-static configuration. This may be trueregardless of whether it is actually used in the subframe. For instance,the UE may be configured to potentially use IS information in subframes0, 1, 2, 4, 5, 6 and 9 of the frame. However, it may not use ISinformation in subframes 3, 7 and 8. In this case, the HARQ informationfor the first group of subframes may be provided in an UL subframe. Forexample, it may be provided 5 subframes later. The HARQ information forthe second group of subframes may be provided in an UL subframe, forexample, 4 subframes later. In UL subframes where HARQ feedback for morethan 1 DL subframe may be provided, HARQ information of the more than 1DL subframe may be bundled or multiplexed. For instance, bundling maytake place in the time domain or between transport blocks of the samesubframe.

In another example, the latency of HARQ feedback may depend on whetherIS information is used in a specific subframe, for instance according toa subset of conditions outlined in the previous section.

The number of HARQ processes may be increased when the UE may beconfigured to operate according to a transmission mode where ISinformation may be used. This may guarantee full resource utilization ina time when the HARQ feedback latency may be increased.

UE Assistance to Trigger NAICS

It may be desirable to limit the potential signaling cost associatedwith indicating to a UE the amount of IS it may expect. Therefore, NAICSmay be performed in cases where a UE's performance may be improved withappropriate interference cancelling and/or suppressing.

A UE may indicate to its serving cell that it may be a victim of highinterference. It may thus indicate that the serving cell should triggerNAICS. In CSI feedback, a new feedback report may indicate highinterference to the network. A simple bit flag may perform such a victimindication. In another example, the report may provide additionalparameters of the IS, such as PMI and or timing (i.e., subframe) of theIS.

In another example, upon feeding back a NACK, a UE may also include anew bit flag indicating the presence of high interference. This mayrequire the serving cell to trigger NAICS. In another example, an eNB,upon reception of multiple NACKS and/or upon determination of a low SINRby a UE, may autonomously decide to trigger NAICS and to configure theUE with IS configurations.

In another example, such a feedback report may also be used to indicatethat interference may no longer be debilitating. It may, thus, indicatethat NAICS may no longer be required. For example, a UE configured viahigher layers with a set of IS may inform its serving cell if itdetermines that one or more of the IS does not actually adversely affectthe performance of the UE.

CSI Reporting

A UE may be configured with new CSI processes, with the intent ofreporting interference. Such modified CSI processes may be configuredfor the UE with limited CSI feedback reporting. For example, the UE mayprovide a single feedback report composed of a single bit (or set ofbits) indicating whether it may experience high interference in such aCSI process. In another example, only RI and/or CQI may be fed back. Inanother example, the PMI may also be fed back. However, in the feedbackreport the meaning of PMI may be to indicate to the network the PMIvalue (or values) that may impede a UE's performance the most.

In another example, CSI feedback may be enhanced such that for every PMIa UE recommends for its desired signal, it may also include a worstpartner PMI. The interpretation of such a worst partner PMI may indicateto the serving cell that a transmission on such a PMI may require NAICS.Alternatively, the interpretation of such a worst partner PMI mayindicate that interference on such a PMI could not be mitigated evenwith NAICS. In another example, the UE may feedback a best partner PMI.Such a PMI may not require NAICS. Alternatively, the best and/or worstpartner PMIs may be a set of PMIs. This may possibly provide moreflexibility for the scheduler.

In another example, a UE may report multiple RIs and/or CQIs for eachband of a CSI process. One RI and/or CQI may inform the serving cell ofthe channel quality without NAICS, and another RI and/or CQI may informthe serving cell of the possible channel quality with NAICS. The RIand/or CQI of the possible channel quality with NAICS may be calculatedwith the assumption that the strongest inter-cell interference signal iscancelled or suppressed. In order to calculate the RI and/or CQI withoutthe strongest inter-cell interference, the strongest inter-cellinterference signal power may be obtained from one or more of CRS,PDSCH, CSI-IM, and CSI-RS of the strongest interfering cell in one ormore subframe. The strongest inter-cell interference signal power may bemeasured in the subframe containing CSI-RS if a UE is configured tomeasure from a CSI-RS. Alternatively, the strongest inter-cellinterference signal power may be measured over multiple subframes.

In another example, a UE may report RI and/or CQI to the serving cellwith NAICS if the UE is configured to perform NAICS receiver and the UEmay report RI and/or CQI to the serving cell without NAICS if the UE isconfigured with a transmission mode without NAICS. Alternatively, a UEmay report RI and/or CQI to the serving cell with NAICS if the UE isprovided with full or partial IS information via higher layer signalingand the UE may report RI and/or CQI to the serving cell without NAICS ifno IS information is provided to the UE.

Thus, a UE may perform measurements of interference on a definedresource (e.g., DM-IM) for demodulation purposes. The UE may estimate anIS from measuring demodulation reference signals used for the IS. Thismay be based on an indication of co-scheduled interference and/ordetection of energy level above a threshold.

The UE may determine the type of modulation scheme used from aconfigured mode of operation. It may also make the determination fromthe value of a field in the received DCI. The UE may obtain ISinformation by decoding a DCI containing the DL assignment correspondingto the IS. The UE may obtain the location of the DCI containing theassignment of the IS from an explicit indication contained in the DCIcontaining its own assignment. The UE may obtain IS information, such asthe identity of an IS, from a DCI encoded in a PDCCH or E-PDCCH separatefrom its own assignment. The UE may provide HARQ feedback pertaining toa DL assignment in a subframe whose timing depends on whether ISinformation is used, or configured to be potentially used, in thesubframe in which the DL assignment may be received, or whether the UEis configured to operate using IS information.

Referring now to FIG. 6 , there is shown a flow diagram of aninterference suppression process 600 for suppressing interference in acommunication system. In interference suppression process 600 a WTRU mayreceive a DM-IM resource as shown in block 602. An interferencemeasurement may be determined based on the DM-IM resource, as shown inblock 604. A received signal may be demodulated based on theinterference measurement as shown in block 606. As shown in block 606 aninterference may be suppressed based on the interference measurement.

Referring now to FIG. 7 , there is shown a flow diagram of aninterference suppression process 700 for suppressing interference in acommunication system. In interference suppression process 700 a receiverof a WTRU may be configured to receive a DM-IM resource, as shown inblock 702. Furthermore, a processor may be configured to determine aninterference measurement based on the DM-IM resource, as shown in block704. The processor may also be configured to demodulate a receivedsignal based on the interference measurement, as shown in block 706. Aninterference may be suppressed based on the interference measurement, asshown in block 708.

Referring now to FIG. 8 , there is shown a flow diagram of aninterference suppression process 800 for suppressing interference in acommunication system. In interference suppression process 800, a WTRUmay receive DL information as shown in block 802. As shown in block 804,a determination may be made from the DL information. The determinationmay be a determination whether a co-scheduling indicator indicates thata further WTRU or transmitter is co-scheduled with the WTRU. An IS ofthe further WTRU may be selectively suppressed based on theco-scheduling indicator, as shown in block 806.

Referring now to FIG. 9 , there is shown a flow diagram of aninterference suppression process 900 for suppressing interference in acommunication system. In interference suppression process 900, energydetection for at least one antenna port not allocated to the WTRU may beperformed, as shown in block 902. As shown in block 904, a determinationmay be made whether the antenna port not allocated to the WTRU has apower level exceeding a threshold. Responsive to the antenna port powerlevel determination it may be established that the antenna port notallocated to the WTRU has an IS, as shown in block 906. The IS may besuppressed as shown in block 908.

One of ordinary skill in the art will understand that many differentembodiments of the foregoing method and devices are possible. Forexample, without any limitations, a method may be implemented by a WTRUincluding receiving a DM-IM resource, determining an interferencemeasurement based on the DM-IM resource, and demodulating a receivedsignal based on the interference measurement. The method may furtherinclude suppressing interference based on the interference measurement,wherein at least one DM-IM resource is located in a PRB. The DM-IMresource may be a plurality of DM-IM resources, the plurality of DM-IMresources may form a DM-IM pattern, and the DM-IM pattern may be locatedon at least one of a Physical Downlink Shared Channel (PDSCH) and/or anenhanced Physical Downlink Shared Channel (E-PDSCH) of at least one LongTerm Evolution (LTE) subframe. The method may also include adjusting aDM-IM pattern in a LTE Resource Block (RB) based on at least one of aframe number associated with the LTE RB, a subframe number associatedwith the LTE RB, and/or an RB index associated with the LTE RB. TheDM-IM resources are different for different Physical Resource Blocks(PRB) in the LTE subframe. The DM-IM resources are located in differentrespective symbols and the locations of the symbols may change relativeto other symbols of the at least one LTE subframe. Receiving the DM-IMresource includes receiving a plurality of DM-IM resources, and/ordynamically adjusting a plurality of DM-IM resources in respective LTEsubframes based on a higher layer signaling, and/or locating a DM-IMresource associated with the WTRU based on a cell specific identifierassociated with a cell serving the WTRU.

A WTRU may receive a Downlink (DL) information and determine, from theDL information, whether a co-scheduling indicator indicates that afurther WTRU or transmitter is co-scheduled with the WTRU. AnInterfering Signal (IS) of the further WTRU or transmitter may beselectively suppressed based on the co-scheduling indicator.

Responsive to the co-scheduling indicator, indicating that the furtherWTRU or transmitter is co-scheduled, locating at least one DemodulationReference Signals (DM-RS) associated with the co-scheduled WTRU ortransmitter, and/or estimating an Interfering Signal (IS) using thelocated DM-RS associated with the co-scheduled WTRU or transmitter, maybe performed.

The DL information includes a Downlink Control Information (DCI), andthe method includes decoding the DL information, including the DCI. Thedetermining includes establishing whether the further WTRU ortransmitter is co-scheduled using the decoded DCI. The DL informationcan include a list of potentially interfering WTRUs or transmitters. TheDL information includes DL assignment information regarding at least onepotentially interfering WTRU or transmitter. The WTRU decodes the DLassignment information of the at least one potentially interfering WTRUor transmitter, and interference canceling and/or suppressing a signalassociated with the at least one potentially interfering WTRU ortransmitter is performed using the DL assignment information.

A method may be implemented by a WTRU including performing energydetection for at least one antenna port not allocated to the WTRU, anddetermining whether the at least one antenna port not allocated to theWTRU has a power level exceeding a threshold. Responsive to thedetermining, establishing that the at least one antenna port notallocated to the WTRU has an Interfering Signal (IS), and suppressingthe IS are performed.

A method may be implemented by a WTRU including receiving DownlinkControl Information (DCI), decoding a mode configuration informationfrom the DCI, and selecting a WTRU operating mode of a plurality of WTRUoperating modes based on the decoded mode configuration information. Theplurality of WTRU operating modes includes a normal operating mode andan enhanced operating mode. The enhanced operating mode is a NetworkAssisted Interference Cancellation and Suppression (NAICS) mode. Theselecting of the enhanced operating mode includes selecting based on aCell Radio Network Temporary Identifier (C-RNTI). In the normaloperating mode, a demodulation used for reception of a downlinktransmission is based on complex-valued modulation. In the enhancedoperating mode, the demodulation used for reception of a downlinktransmission is based on only real valued modulation. Different WTRUoperating modes are selected based on changing mode configurationinformation.

A method can be implemented by a WTRU including receiving a DownlinkControl Information (DCI) of the WTRU and a DCI of an Interfering Signal(IS) associated with at least one further WTRU or transmitter,determining, in the DCI of the WTRU, an IS assignment indicator forindicating a location of the DCI of an IS assignment, and locating,based on an IS assignment indicator, the DCI of an IS associated withthe at least one further WTRU or transmitter. The IS assignmentindicator is located in at least one of a Network Assisted InterferenceCancellation and Suppression (NAICS), a starting index of an EnhancedControl Channel Element (ECCE) of the DCI, or an aggregation level ofthe ECCE. The WTRU determines the IS assignment indicator information inthe DCI. The WTRU makes a determination that the DCI is present in apredetermined search space in a current transmission to provide a DCIpresent determination, and/or a determination that the IS assignmentindicator is present in the current transmission based on the DCIpresent determination.

A method may be implemented by a WTRU including receiving DownlinkControl Information (DCI) of an Interfering Signal (IS) associated withat least one further WTRU or transmitter, decoding the DCI using a cellspecific identifier common to the WTRU and/or the at least one furtherWTRU or transmitter, determining, from the decoded DCI, InterferingSignal (IS) information including a strongest interferer informationregarding the strongest interferer of the at least one further WTRU ortransmitter, determining a further cell specific indicator for thestrongest interferer based on the strongest interferer information; anddecoding downlink scheduling information of the strongest interfererusing the further cell specific indicator. The DCI further includesNetwork Assisted Interference Cancellation and Suppression (NAICS)information. Decoding Physical Downlink Control Channel (PDCCH)information or Enhanced Physical Downlink Control Channel (E-PDCCH)information based on the NAICS information, and decoding a DownlinkShared Channel (PDSCH) based on the NAICS information, are performed.

A method can be performed by a WTRU including determining first and/orsecond latencies for transmission of a HARQ feedback associated withreception of a PDSCH based on whether an IS information for the PDSCH isreceived, transmitting the HARQ feedback in a first subframe based onthe first latency when the IS information for the PDSCH is received, andtransmitting the HARQ feedback in a second, different, subframe based onthe second latency when the IS information for the PDSCH is notreceived. The first and/or second latency are determined based onwhether the IS information is used. The first and/or second latency aredetermined based on a modulation scheme. The contents of the RP-130404,“Study on Network-Assisted Interference Cancellation and Suppression forLTE”, 3GPP TSG RAN Meeting #59, February 2013, 3GPP TS 36.211, “PhysicalChannel and Modulation”, V11.2.0, 2013-02, 3GPP TS 36.212, “Multiplexingand Channel Coding”, V11.2.0, 2013-02, 3GPP TS 36.213, “Physical LayerProcedures”, V11.2.0, 2013-02, and R1-131547 Network Assistance forInterference Cancelation for CRE; Ericsson, ST-Ericsson, are herebyincorporated by reference. Although features and elements are describedabove in particular combinations, one of ordinary skill in the art willappreciate that each feature or element can be used alone or in anycombination with the other features and elements. In addition, themethods described herein may be implemented in a computer program,software, or firmware incorporated in a computer-readable medium forexecution by a computer or processor. Examples of computer-readablemedia include electronic signals (transmitted over wired or wirelessconnections) and computer-readable storage media. Examples ofcomputer-readable storage media include, but are not limited to, a readonly memory (ROM), a random access memory (RAM), a register, cachememory, semiconductor memory devices, magnetic media such as internalhard disks and removable disks, magneto-optical media, and optical mediasuch as CD-ROM disks, and digital versatile disks (DVDs). A processor inassociation with software may be used to implement a radio frequencytransceiver for use in a WTRU, UE, terminal, base station, RNC, or anyhost computer.

1-20. (canceled)
 21. A method implemented by a wireless transmit/receiveunit (WTRU), comprising: receiving, in downlink control information(DCI), (1) information indicating a set of resource elements (REs)corresponding to reference signals, the reference signals used fordemodulation of a physical downlink shared channel (PDSCH) transmissionand (2) an indicator indicating additional REs correspond to additionalreference signals, the additional reference signals also used fordemodulation of the PDSCH transmission, the additional reference signalscontaining no PDSCH data; determining positions in time and frequency ofthe REs and the additional REs based on the received DCI; receiving thePDSCH transmission; and decoding the PDSCH transmission.
 22. The methodof claim 21, wherein the receiving of the PDSCH transmission includesrate matching the PDSCH around the determined positions in time andfrequency of the REs and the additional REs to exclude the REs and theadditional REs from the reception of the PDSCH.
 23. The method of claim21, wherein the received information in the DCI indicates at least someof the reference signals used for demodulation correspond to, contain,or are reserved for DM-RS transmission intended for the WTRU.
 24. Themethod of claim 21, wherein at least some of the reference signals usedfor demodulation correspond to, contain, or are reserved for aco-scheduled DM-RS transmission.
 25. The method of claim 21, wherein allof the reference signals used for demodulation correspond to, contain,or are reserved for DM-RS transmission intended for the WTRU orco-scheduled DM-RS transmission.
 26. The method of claim 21, wherein theREs corresponding to the reference signals are orthogonal in frequency.27. The method of claim 21, wherein the DCI includes any of: (1) one ormore parameters indicating a pattern associated with the set of REs or(2) a value or an indication of the value indicating the patternassociated with the set of REs.
 28. The method of claim 27, wherein theREs associated with the indicated pattern are adjacent REs in a resourceblock.
 29. The method of claim 27, wherein the REs associated with theindicated pattern are a fixed number of REs within a resource block. 30.A wireless transmit/receive unit (WTRU), comprising: a transmit/receiveunit configured to: receive, in downlink control information (DCI), (1)information indicating a set of resource elements (REs) corresponding toreference signals, the reference signals used for demodulation of aphysical downlink shared channel (PDSCH) transmission and (2) anindicator indicating additional REs correspond to additional referencesignals, the additional reference signals also used for demodulation ofthe PDSCH transmission, the additional reference signals containing noPDSCH data, and receive the PDSCH transmission; and a processorconfigured to: determine positions in time and frequency of the REs andthe additional REs based on the received DCI, and decode the PDSCHtransmission.
 31. The WTRU of claim 30, wherein the WTRU is configuredto rate match the PDSCH around the determined positions in time andfrequency of the REs and the additional REs to exclude the REs and theadditional REs from the reception of the PDSCH.
 32. The WTRU of claim30, wherein at least some of the reference signals used for demodulationcorrespond to, contain, or are reserved for DM-RS transmission intendedfor the WTRU.
 33. The WTRU of claim 30, wherein at least some of thereference signals used for demodulation correspond to, contain, or arereserved for a co-scheduled DM-RS transmission.
 34. The WTRU of claim30, wherein all of the reference signals used for demodulationcorrespond to, contain, or are reserved for DM-RS transmission intendedfor the WTRU or co-scheduled DM-RS transmission.
 35. The WTRU of claim30, wherein the REs corresponding to the reference signals areorthogonal in frequency.
 36. The WTRU of claim 30, wherein the DCIincludes any of: (1) one or more parameters indicating a patternassociated with the set of REs or (2) a value or an indication of thevalue indicating the pattern associated with the set of REs.
 37. TheWTRU of claim 36, wherein the REs associated with the indicated patternare adjacent REs in a resource block.
 38. The WTRU of claim 36, whereinthe REs associated with the indicated pattern are a fixed number of REswithin a resource block.